Heat supply system and means for engine choke control



1955 P. M. ROTHWELL 2,757,652

HEAT SUPPLY SYSTEM AND MEANS FOR ENGINE CHOKE CONTROL Filed NOV. 13, 1951 3 Sheets-Sheet 1 INVENTOR; fizzy zozzwezi.

1956 P. M. ROTHWELL 2,757,652

HEAT SUPPLY SYSTEM AND MEANS FOR ENGINE CHOKE CONTROL Filed Nov. 13, 1951 3 Sheets-Sheet 2 P. M. ROTHWELL Aug. 7, 1956 HEAT SUPPLY SYSTEM AND MEANS FOR ENGINE CHOKE CONTROL Filed Nov. 13. 1951 3 Sheets-Sheet 3 IN V EN TOR. fiizfi M yo]; zz/e/Z x W /W.

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United States Patent HEAT SUPPLY SYSTEM AND MEANS FOR ENGINE CHOKE CONTROL Philip M. Rothwell, Detroit, Mich, assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Application November '13, 1951, Serial No. 255,907

13 Claims. (Cl. 123-55) ciated, is at a predetermined low temperature, and to gradually open the choke valve as the engine warms up to a predetermined high temperature at which the choke valve is retained in open position. v

Customarily, the carburetor has the choke valve control built into it and includes a temperature-responsive element heated by a stream of warm air drawn by manifold suction into the choke device where it impinges upon the temperature-responsive element and is thence drawn to the carburetor mixing chamber for intermixing with the fuel.

More recently, as shown in the application of Frederick Osann, Jr., Serial No. 220,493, filed April 11, 1951, the warm air is impinged on a metallic heat-absorbing body or stove built into the control, which stove warms the temperature-responsive element by heating the air adjacent thereto. This method of heating the temperatureresponsive element requires more heat supply than where the temperature-responsive element is directly heated by the hot air.

In some prior heat supply systems, the heated air has been conducted to the built-in choke devices through a length of tubing, the air intake end portion of which extends across the transverse section of a tubular exhaust pipe and projects outwardly therefrom to enable the open end of the tube to draw in surrounding air. In other instances, the tube has been associated with a heating stove seated on the exhaust manifold.

Usually the point of heating the indrawn air has been some distance away from the choke device and because of the limited available heat and great heat losses this has required that the tube be insulated by suitable wrapping against excessive heat loss. Moreover, the intake end of the tube hasalso usually been located 'at a position in relation to the engine where the surrounding air to be indrawn is of variable temperature, by reason of the constant displacement of the air by the engine fan.

In the case of V-type engines, the quantity of exhaust gas available at the exhaust header or pipe for heating air to be conducted to a choke device is less than in a line engine, since in the first case the exhaust gas volume is that usually provided by one bank of cylinders, usually four in number, instead of six or eight cylinders as in a line engine. Moreover, in the line engine theexhaust manifold is also usually directly under the carburetor so that there is less heat loss. Hence a problem :arises'in connection with V engines to provide a heatsupply system which may furnish suflicient heated air tothe choke device to enable its proper functioning. I

The principal object of this invention is to overcome 2,757,652 Patented Aug. 7, 1956 vice the previously discussed difificulties and problems and provide a satisfactory arrangement for supplying a heated fluid medium to the choke control device.

Another object is to provide a heat supply means in close proximity to the hottest portion of the available exhaust gas and as nearly as possible to the choke control device, to thereby facilitate a rapid heat exchange between the exhaust gas and the fluid medium, usually air, to be heated and by it transmit to the choke device a maximum amount of heat in the shortest possible time.

Another object is to provide a heating means for automatic chokes that includes an exhaust gas passage and an air-conducting tube positioned therein in a manner to obtain the maximum tube heating surface for effecting a transfer of heat from the exhaust gas to the air flowing within the tube. 1

Still another object is to provide a heat supply system or meansfor an automatic choke control having a built-in warm-up stove for the temperature-responsive element, which means is capable of rapidly heating the choke stove to enable satisfactory control of the choke during engine warm-up.

An additional object is to provide a heat supply system or means for V engines comprising a heat supply element or member preferably a tube, positioned in an exhaust carrying cross passage of the intake manifold of the engine.

A further object is to provide a heat supply means as in the precedingobject wherein the exhaust gas inlet for the heating passage is on the same side of the engine as the heat supply tube. 5

An additional object is to provide a heat supply system or means providing suflicient heat capacity to prevent the choke from coming back on after going off, in the event of temporary reduction of heated exhaust gas flowing to the chamber containing the heat supply structure as by reason of temporary reduction of heat flow due to normal opening of the heat valve. I

It is also an object to provide a heat supply means or system for automatic chokes that includes a chamber supplied with exhaust gas and a tubular air-conducting member positioned within the chamber, and wherein the chamber is provided with a baflie wall means for causing the exhaust gas to sweep the floor of the chamber and circulate about the tube to facilitate rapid heating of the air in the tube.

A further object is to provide a manifolding structure for V engines having a cross hot spot passage connecting the main exhaust gas passages at the right and left sides of the engine to facilitate rapid heating of a choke heat supply tube arranged in the cross passage and which cross passage is arranged immediately below the intake passage of the manifold to facilitate heating of the lower floor of the intake passage.

A further object is to provide a heat supply means for automatic choke controls comprising an elongated tubular air-conducting heat exchange member positioned in the hot zone of the exhaust system and so shaped as to cause the air to traverse the hot zone a plurality of times.

Aspecific object of the invention is to provide a heat supply means as in the preceding object wherein the tubular member is a U-shaped member to provide two airconducting branches and which shaping permits the inlet and outlet ends of the supply means to be positioned adjacent the carburetor choke control device and thereby reduce to a minimum the heat loss in conducting the air from the member to the control device.

A further specific object is to provide heat supply means including a tubular element wherein the air inlet end of the tubeis bent down to face the exterior surface of the engine'and in position out of the direct influence of the 2,757,662 I I I engine fan whereby to avoid substantial fluctuation in the temperature of the air drawn into the element.

Further objects and advantages of my invention will become apparent from the following description and from the accompanying drawings wherein:

Figure l is a transverse section illustrating my invention as applied to a V-type engine, the heat supply tube being shown as arranged in a crossover passage connecting the longitudinal exhaust gas headers of the engine;

Figure 2 is a longitudinal elevational view of the upper portion of the engine of Figure 1 showing the heat supply tube and its air inlet in relation to the engine surface, the carburetor and the engine fan;

Figure 3 is a top plan view of a fragmentary portion of the engine of Figures 1 and 2 showing the heat supply tube connection with the carburetor choke control device and showing the inlet end of the supply tube in relation to certain wall portions of the crossover passage on which the tube is mounted; and

Figure 4 is a top view of the engine intake and exhaust system showing the intake manifold passages and including a schematic sectional showing of the exhaust gas passages.

In the drawings in which like reference numerals designate corresponding parts of the structure, I have illustrated my invention as applied to an 8-cylinder V-type engine of current manufacture. The engine as seen in Figures 1 and 4, has right and left cylinder banks 10 and 12 respectively, each containing four cylinders 14. The cylinder banks are arranged in a V relationship and the cylinders of the two banks staggered relative to each other. The axes of the cylinders of the banks when projected, intersect in the longitudinal axis of the engine crankshaft 16. Movable in the cylinders 14 are pistons 18 operably connected to offset portions or cranks 19 of the crankshaft 16 by connecting rods 20.

The cylinder heads of each bank of cylinders are generally designated by the numeral 21, and are provided with transversely arranged intake and exhaust valves 22 and 24 respectively, operated through rocker arms, of which the exhaust valve rocker arms 26 only are shown, which arms are actuated through lift rods 28, 29 by a camshaft 30 suitably driven from the crankshaft 16.

As seen in Figures 1 and 4, each cylinder head has transversely extending parallel exhaust gas passages 32, 34, 36, and 38, which connect the exhaust valves 24 of the cylinders with longitudinally extending collection headers 40, 42 suitably secured to the outer side of the cylinder heads of the right and left cylinder banks respectively. The right header 40 has a central outlet passage 44 in the form of a downward pipe extension 45 located intermediate the cylinder group of the right bank, and the left header has a similar outlet passage 46 provided by a downward pipe extension 47 of the header 42 and similarly positioned intermediate the cylinder group of the left bank.

An exhaust gas conduit or tube 48 connects with the extension 45 through a heat valve 50 of known construction capable of controlling the temperature and velocity of the exhaust gas passing from the header 40 to the mufller. It is provided with a diaphragm 51, thermostatically controlled, which is normally closed when the engine is cold and permits the exhaust gas to be shunted across the intake manifold as hereinafter described. The pipe 48 extends downwardly and connects in a T fitting 52 as also does similar pipe 54 which connects the pipe 47 of the header 42. As seen, the pipe 54 projects downwardly from the extension 47, passes beneath the engine transversely thereof, and connects by a longitudinal branch with the fitting 52. A further pipe, not shown, connects with the T fitting opposite the longitudinal branch of the pipe 54 and extends to a mufiler, not shown.

A tortuous cross passage, generally designated by the.

4 numeral 56 and formed in part in the intake manifold member 58 and part in the cylinder heads 21 of cylinder banks 10 and 12, connects, as seen for example in Figures 1 and 4, the exhaust valve passages 34 and 36 of one bank with the similar exhaust valve passages of the other bank.

As seen in Figure 4, the portions 59 of the aforesaid cross passage located in the cylinder heads 21 form the legs of Ts with the exhaust valve passages 34 and 36. Moreover, the portion of the exhaust gas crossover passage formed as part of the intake manifolding 58 comprises, as seen in Figures 1 and 4, a central passage, chamber, or compartment 60 of generally Z-shape extending longitudinally of the transverse passage and having a generally rectangular section transversely of the passage. This Z-shaped portion is formed with an upper horizontal branch portion 61, a lower horizontal branch or portion 62, and a connecting vertical portion 63, the floor of these portions forming a stepped surface 64 and the ceiling 66 being likewise invertedly. stepped.

The branch 61 of chamber 60 is connected at the right side of the engine with a further passage, chamber, or compartment 67, which chamber is of rectangular cross section and narrower transversely than the chamber 60. The chamber 67 has a funnel-shaped portion 68 which extends downwardly from the floor of the branch 61 of the chamber 60 to seat as at 68 with the inner side of the cylinder head 21 of the right cylinder bank and has an opening 69 which connects with the crossover passage portion 59 in the head 10.

The branch 62 of the chamber 60 is connected at the left side of the engine with a passage, chamber, or compartment 70. The chamber 70 has a transverse rectangular section, and like the chamber 67 is narrower than the chamber 60 transversely of the passage but is offset from the chamber 67. The chamber 70 in part starts from a point above the ceiling 66 of the chamber 60 and tapers downwardly to a point below the branch 62 of the chamber 60 to seat as at 71 against the inner side of the cylinder head 21 of the left cylinder bank 12. The chamber 70 has an opening 72 which connects with the portion 59 of the crossover passage 56 in the cylinder head 21 of the bank 12.

It will be noted from Figure 1 that the ceiling wall 66 of the passage 60 as well as the vertical walls 73, 74 of the chambers 67 and 70 respectively, also provide walls for. the intake manifold fuel passages 75 and 76 such that the fuel air mixture passing through the passages 75, 76 is heated by the exhaust gases passing through the crossover passage 56, particularly in the region of the aforesaid wall and ceiling portions of the chambers 60, 67, and 70.

Each of the chambers 67 and 70 is also preferably provided with vertical walls 78, 80 extending upwardly from the floor of the chambers 67 and 70 respectively, a portion of the height of these chambers respectively. These walls serve as bafiies to retard movement of the exhaust gases through the tortuous cross passage from the right to the left side of the engine or vice versa such that the exhaust gas will be caused to give up as much heat as possible in its movement to the walls of the crossover passage and to the surface of a member generally designated by the numeral 82 to which further reference will be hereinafter made, which projects into the chambers 59 and 67 of the crossover passage 56.

The chamber 67 has side walls 84, 86 (Figure 4) which project laterally from the intake manifold (Figure 3) and terminate in a side or lateral wall 88. These walls together with a further wall 87, extend downwardly to form the hereinabove mentioned seat 68 of the chamber 67 connecting with the exhaust passage or chamber 59 in the cylinder head 21.

The crossover passage 56 is also provided in the chamber 67 with a top wall 90 having a machined face 92 in a common plane with a face 96 of the intake manifolding tnember 58 whose passages 75 and 76 have vertical inlets 98 and 100 opening into the machined face 96 where they connect with complementary passages in a dual downdraft carburetor 102 seated upon the face 96.

The wall 90 is provided with an aperture 104 opening into the chamber 67. The opening is closed by a cover member 106, seated on the face 96 and secured by suitable fastening means such as screws 108 to the wall 90. This cover member supports the heat supply or transfer member or element 82. The member 82 is preferably formed of tubular material, preferably a heat and gas resistant steel or alloy steel, for instance stainless steel, and preferably capable of resisting the corrosive effect of the gases at sustained temperatures of 700 F.

As seen in Figures 1 and 4, the member 82 is of a hairpin-like or U-shape and has tubular legs 112, 114 preferably of circular section which extend generally parallel to each other and terminate in a bulbous tip portion 116 formed by a bend of substantial radius. These legs provide adjacent air-conducting passages 118, 120 in which the air in one will flow in opposite direction to the air in the other. The legs 112, 114 preferably lie in the plane of the crossover passage 56 and extend downwardly from the cover into the chamber 67 through the opening 68 and into the chamber 59 of the cylinder head 21 at the right bank of the engine. legs 112, 114 extend vertically downwardly from the cover and then curve and slope diagonally outwardly from the chamber 67 into the chamber 59. These leg portions are, moreover, arranged to preferably lie in the central portion of the chambers 59 and 67.

The leg 112, which may be termed the inlet branch of the member 82 extends through the cover and is formed outside the cover with a hook or inverted bent portion 122 (see Figure 2), which extends at generally right angles to a plane containing the legs 112, 114 and furthermore,

hooks over and extends downwardly adjacent the rearward wall 84 of the chamber 67 with its open end 132 facing the exterior surface of the intake manifoldmember 58.

The branch or leg 114 which may be denominated the output branch of the member 82, also passes through the cover 106 and has by preference a projecting tip which is preferably connected by means of a flexible or bendable tube 123 with the chamber 124 of the choke control unit 126. The heating chamber may contain temperatureresponsive element 128 which is to receive direct heating by the air delivered by the member 82, or may, as seen in Figure 1 and more fully disclosed in the aforesaid application Serial No. 220,493, contain a heating stove or heat It will be observed that the absorption member 130 which in turn imparts heat to the I temperature-responsive element'128. The choke control includes passage means which connects through other passages with the carburetor mixing chamber.

In operation of the heating system, air is drawn in at the open end 132 of the bent portion 122 of the input leg 112 of the member 82, by means of manifold vacuum created at the carburetor mixing chamber through downward movement of the pistons 18, and is sucked through the tubular passages 118, 120 of the member 82 into the heating chamber 124 of the choke control device 126 and thence into the carburetor mixing chamber where it mixes with the fuel. As the air traverses the passages 118, 120, heat is transferred from the hot gases in the chamber 67 to this air through the metallic body of the member 82. By reason of the shaping of member 82, it will be evident that the air traverses the hot gases of the chamber 67 and passage 59 at least twice, and a greater number of times if more than two legs are provided for the structure.

The described formation of the member 82 is particularly advantageous since it provides an extended passageway for the air in the hottest portion or hot spot of the crossover passage 56, and hence enables the transfer of a greater amount of heat to the air in the tubular passages. It will be noted that when the cold engine is started, the

heat valve is closed and hence the initial exhaust gases collected in the header 40 cannot pass through the pipe 48 but must back-track through the chambers 59, 60, 67, and of the crossover passage 56. Some hot gases may also move from the exhaust header 42 back through the passage 59 at the left side of the engine and into the chamber 70, but the major portion thereof at this side will go down through the pipe 54 to the muffler. As the hot exhaust gases are forced back through the passage 59 at the right side of the engine into the chamber 67, they strike the batlle 78 and are thrown back to re-contact and circulate around the entire length of the 'leg portions 112, 11.4 of the member 82 thus assuring a maximum heat transfer to the air traversing the member 82.

It will also be noted that the air intake end 132 of the member 82 is shielded from the path of the engine fan 134 by the walls 84, 86, 88 and hence is able to suck in air of substantial uniform heat condition adjacent the surface of the engine.

While it will be apparent that the illustrated embodiment of my invention is well calculated to adequately fulfill the objects and advantages described above, it is to be understood that the invention is susceptible to variation, modification, and change within the spirit and scope of the appended claims.

I' claim:

1. In a V type engine having a pair of V-arranged cylinder heads, aligned exhaust valves at the outer engine sides of said heads, a carburetor, an intake manifold intermediate said heads and mounted thereon, a fan at the forward end of said engine driven thereby, and an automatic choke control device; a heat supply system for supplying heated air to said device comprising exhaust valve passages ex tending from said valves to said outer sides, a cross passage in each heat connecting with a pair of said exhaust valve passages therein and extending to the opposite side of said head, an exhaust gas header secured to the outer side of each head and connecting with the exhaust valve passages of the head to which it is secured, an exhaust gas pipe connecting each header with a third pipe, a heat control valve in one of said exhaust gas pipes intermediate its header and said third pipe, a tortuous cross passage in said intake manifold structure connecting with the said cross passages ofsaid heads, a chamber in said passage defined by wall portions of said intake manifold including front and rear wall portions projectinglaterally from said manifold adjacent said carburetor, said rear wall portion forming with other adjacent wall portions of said manifold, an angular air pocket substantially free of the influence of air drafts from said fan, an opening in the top of said chamber, a cover closing said opening, a metallic heat exchange member of U shape mounted in said cover andextending into said chamber, the end of one leg of said member extendingthrough said cover and including a portion turned down toface said manifold structure adjacent said rear wall of said chamber and the end of the other leg of said member extending through said cover and there being means connecting it with said choke control device. 7

2. A heating system for delivering hot fluid medium to the temperature-responsive choke control means of a V engine having an exhaust manifold and an intake manifold on which a carburetor carrying said choke control means is mounted, comprising a heating chamber extending transversely of the engine in the intake manifold thereof, said chamber being close to said carburetor, passage means connecting said chamber with the engine exhaust manifold for receiving hot exhaust gases therefrom, a heat exchange member of tubular character positioned in said chain ber below said choke control means to be directly ex posed to said hot exhaust gases, said member having an inlet for receiving fluid medium from a source thereof externally of said engine, an outlet for connection with said choke control means, and passage means defined by said tubular structure for conducting said fluid medium between said inlet and said outlet, a portion of said passage means providing for flow of said fluid medium in a direction opposite to that in another portion thereof.

3. A heating system for delivering a hot fluid medium to the temperature-responsive choke control means of a V engine having an exhaust manifold and an intake manifold on which a carburetor carrying said choke control means is mounted, comprising a heating chamber extending transversely of the engine in the intake manifold thereof, said chamber being close to said carburetor, passage means connecting said chamber with the engine exhaust manifold for receiving hot exhaust gases there through, an elongated heat exchange member positioned in said chamber below said choke control means to be directly exposed to said hot exhaust gases, said member having an inlet for receiving fluid medium from a source thereof exteriorly of said intake manifold structure and having an outlet for connection with said choke control means and said member having laterally adjacent elongated portions providing a continuous passage for said fluid medium between said inlet and said outlet.

4. A heating system for delivering a hot fluid medium to the temperature-responsive choke control means of a V engine having an exhaust manifold and an intake manifold on which a carburetor carrying said choke control means is mounted, comprising a heating chamber extending transversely of the engine in the intake manifold thereof, said chamber being close to said carburetor, passage means connecting said chamber with the engine exhaust manifold for receiving hot exhaust gases therethrough, a tubular metallic heat exchange member of generally elongated U-shape positioned in said chamber below said choke control means to be directly exposed to said hot gases, said member having one leg thereof opening into a source of said fluid medium located exteriorly of said intake manifold structure and having the other leg thereof connected with said choke control means.

5. A heating system as claimed in claim 4 wherein the end of said tubular member at the base of said U is of a bulbous character.

6. A heating system for delivering hot air to the temperature-responsive choke control means of a V engine having an exhaust manifold and an intake manifold on which a carburetor carrying said choke control means is mounted, comprising a heating chamber extending transversely of the engine in the intake manifold thereof, said chamber being close to said carburetor, passage means connecting said chamber with the engine exhaust manifold for receiving hot exhaust gases therefrom, a tubular metallic heat exchange member of generally elongated U-shape positioned in said chamber below said choke control means to be directly exposed to said hot exhaust gases, whereby to heat air passing through said member, said member having one leg thereof opening into a source of air at a point in juxtaposition to said intake manifold structure and exteriorly thereof and having its other leg Z' extending exteriorly of said intake manifold structure and connecting with said choke control means.

7. A heating system for delivering hot air to the temperature-responsive choke control means of a V engine having an exhaust manifold and an intake manifold on which a carburetor carrying said choke control means is mounted, the said choke control means including a builtin stove to be heated by said hot air, comprising a heating chamber extending transversely of the engine in the intake manifold thereof, said chamber being close to said carburetor, passage means connecting said chamber with the engine exhaust manifold for receiving hot exhaust gases therethrough, an opening in said intake manifold below said choke control means connecting with said chamber, a cover for closing said opening, a tubular metallie heat exchange member of generally elongated U-shape carried by said cover and extending through said opening into said chamber to be directly exposed to said hot ex haustgases, said member being adapted to conduct air heated in its passage therethrough from a location ambient said intake manifold structure to said choke control stove, the leg portions of said U member projecting outwardly from said cover, one of said projecting leg portions being of inverted U-shape and having the end thereof opening into said ambient air immediately adjacent said cover and tubular means connecting the other projecting leg portion of said U member with said choke control stove.

8. A heating system for delivering hot air to the temperature-responsive choke control means of a V engine having an exhaust manifold and an intake manifold on which a carburetor carrying said choke control means is mounted, comprising a heating chamber in the intake manifold structure of said engine, said chamber being close to said carburetor, passage means connecting said chamber with the exhaust manifold of said engine for receiving hot exhaust gases therefrom, said chamber having an exhaust gas inlet opening at the bottom thereof, an exhaust gas outlet opening intermediate the top and bottom of said chamber and having a third opening in the top of said chamber below said choke control means, the lower portion of said chamber extending downwardly away from said outlet opening toward said inlet opening, a cover mounted on said intake manifold structure and closing said third opening of said chamber, a tubular metallic heat exchange member of generally elongated U- shape carried by said cover and extending into said chamer to adjacent the exhaust inlet thereof to be directly exposed to the hot exhaust gases received in said chamber, said member being adapted to conduct air heated in its passage therethrough from a location ambient said intake manifold structure to said choke control means, said member having a portion generally normal to said cover and another portion sloping downwardly and obliquely from said first portion in conformity with the lower portion of said chamber, the leg portions of said U member extending through said cover and projecting from the top thereof, one leg portion of said U member having its projecting end shaped in the form of an inverted U-shape and opening into said ambient air, and means connecting the projecting end of the other leg of said U member with said choke control means.

9. A heating system for delivering hot air to the temperature-responsive choke control means of a V engine having an exhaust manifold and an intake manifold on which a carburetor carrying said choke control means is mounted, comprising a heating chamber in the intake manifold structure of said engine, said chamber being close to said carburetor, passage means connecting said chamber with the exhaust manifold structure of said engine for receiving hot exhaust gases therefrom, said chamber having an exhaust gas inlet opening at the bottom thereof, an exhaust gas outlet opening intermediate the top and bottom of said chamber, and the lower portion of said chamber sloping downwardly and away from said outlet toward said inlet, a baffie wall in said chamber spaced from said inlet opening and confronting the same, and a tubular heat exchange member positioned in said chamber below said choke control means and extending through said inlet opening thereof into said passage means to be directly exposed to the hot gases therein, said member being adapted to conduct air heated in its passage through said member from a location ambient said intake manifold structure to said choke control means, said member having an inlet end extending exteriorly of said chamber and opening into said ambient air and said member having an outlet end extending exteriorly of said chamber connecting with said choke control means.

10. A heating system for delivering hot air to the temperature-responsive choke control means of an engine having opposite cylinder banks arranged in a V and having an exhaust manifold and an intake mnifold on the latter of which a carburetor carrying said choke control means is mounted, comprising a tortuous heating chamber extending transversely of the engine between the opposite cylinder banks thereof in the intake manifold structure thereof, said chamber being close to said carburetor, passage means connecting said chamber with the engine exhaust manifold structures of each bank, an exhaust gas conductor member connecting each exhaust gas manifold structure with a third conductor member, a heat control valve in one of said exhaust gas conductor members intermediate its exhaust manifold structure and said third conductor member, said heat valve adapted to control the flow of hot exhaust gases between said exhaust manifold structures through said tortuous heating chamber, a metallic heat exchange member positioned in said chamber below said choke control means to be directly exposed to said hot exhaust gases, said heat exchange member being adapted to conduct air heated in its passage through this member from a location ambient said intake manifold structure to said choke control means, said heat exchange member having an inlet end and an outlet end, said inlet end extending exteriorly of said chamber and having its end opening into the ambient air at a position substantially close to the surface of said engine and said outlet end extending exteriorly of said chamber and connecting with said choke control means.

11. A heating system for delivering hot air to the temperature-responsive choke control means of an engine having opposite cylinder banks arranged in a V and having an exhaust manifold and an intake manifold on the latter of which a carburetor'carrying said choke control means is mounted, comprising a tortuous heating chamber in said intake manifold structure of said engine, said chamber being close to said carburetor, passage means connecting said chamber with the exhaust manifold structure of the opposite banks of said engine for conducting hot exhaust gases to said chamber, a heat control valve for controlling the flow of exhaust gases between said exhaust manifolds through said chamber, a tubular metallic heat exchange member positioned in said heating chamber below said choke control means to be directly exposed to said hot gases, said member being adapted to conduct air heated in its passage through said member from a location ambient said engine to said choke control means, said member having an inlet end and an outlet end, both said ends projecting exteriorly of said intake manifold structure, said inlet end being open to the ambient air adjacent said intake manifold structure and said outlet end connecting with said choke control means.

12. A heating system for delivering hot air to the stove of a temperature-responsive choke control means of a V engine having an exhaust manifold and an intake manifold on-which a carburetor carrying said choke control means is mounted, comprising a tortuous heating chamber extending transversely of the intake manifold structure of said engine, said chamber being close to said carburetor, passage means connecting said chamber with the exhaust manifold structure of each bank of the engine, an exhaust gas pipe connecting each exhaust gas manifold with a third pipe, :1 heat control valve in one of said exhaust gas pipes between its exhaust gas manifold and said third pipe, a metallic heat exchange member of generally U-shape positioned in said chamber below said choke control means to be directly exposed to hot exhaust gases conducted thereto from said exhaust gas manifolds, said member being adapted to conduct air heated in its passage through said member from a location ambient said engine to said choke stove, said member having both of its legs extending exteriorly of said intake manifold structure and one leg opening into said ambient air and the other connecting with said choke stove.

13. A heating system for delivering hot air to the temperature-responsive choke control means of a V engine having a rotary fan at the forward end thereof and driven thereby and having an exhaust manifold and an intake manifold on which a carburetor carrying said choke control means is mounted, comprising a heating chamber in said intake manifold structure, said chamber being close to said carburetor, passage means connecting said chamber with the exhaust manifold structure of the opposite banks of said engine for conducting hot exhaust gases to said heating chamber, a projection externally of said intake manifold structure below said choke control means forming an angular air pocket shielded by said projection from the direct influence of the air current from said fan, a metallic heat exchange member positioned in said chamber below said choke control means and operable for conducting air heated in its passage through this member to said choke control means, one end of said member extending exteriorly of said chamber and opening into said angular air pocket and the other end thereof connecting with said choke control means.

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